An internal combustion engine which comprises a supercharger control device capable of controlling the supercharging amount or the supercharging pressure of a super charger provided with a variable flow mechanism, and an exhaust gas recirculation (EGR) apparatus which recirculates a part of the exhaust gas into an intake passage or a cylinder, is known. In such an internal combustion engine, particularly in a diesel engine, by controlling the supercharger provided with a variable flow mechanism, the discharge pressure is increased and then the recirculation amount of the exhaust gas by EGR is increased, whereby the intake flow and the supply air oxygen concentration will not be ensured, and thus smoke (PM) will be increasingly generated; or the discharge pressure is decreased, whereby the recirculation amount of the EGR gas will not be ensured, and thus an effect of reducing NOx will not be obtained, for example. That is, there is a relationship between the control of EGR and the control of the supercharger provided with a variable flow mechanism where they have influence on each other.
In this regard, a technique of controlling the EGR control and the supercharger control in a coordinated manner is known. An example of coordinate control of this type is described in Patent Document 1. In Patent Document 1, it is disclosed that in a operating region where exhaust gas recirculation (EGR) is carried out, by feeding back the EGR control valve so as to bring the air-fuel ratio to the target air-fuel ratio while adjusting the opening degree of the variable flow mechanism to be within a predetermined range, it is possible to reduce NOx and PM.